Enzymatic characterization, molecular dynamics simulation, and application of a novel Bacillus licheniformis laccase

A new laccase gene from newly isolated Bacillus licheniformis TCCC 111219 was actively expressed in Escherichia coli. This recombinant laccase (rLAC) exhibited a high stability towards a wide pH range and high temperatures. 170% of the initial activity was detected at pH 10.0 after 10-d incubation, and 60% of the initial activity was even kept after 2-h incubation at 70 degrees C. It indicated that only single type of extreme environment, such as strong alkaline environment (300 K, pH 12) or high temperature (370 K, pH 7), did not show obvious impact on the structural stability of rLAC during molecular dynamics simulation process. But the four loop regions of rLAC where the active site is situated were seriously destroyed when strong alkaline and high temperature environment existed simultaneously (370 K, pH 12) because of the damage of hydrogen bonds and salt bridges. Moreover, this thermo- and alkaline-stable enzyme could efficiently decolorize the structurally differing azo, triphenylmethane, and anthraquinone dyes with appropriate mediator at pH 3.0, 7.0, and 9.0 at 60 degrees C. These rare characteristics suggested its high potential in industrial applications to decolorize textile dyeing effluent. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

A newly isolated laccase gene from Bacillus licheniformis TCCC 111219 was expressed efficiently in Escherichia coli, showing high stability towards various pH levels and temperatures. However, simultaneous exposure to strong alkaline and high temperature environments resulted in significant damage to the active site loop regions of the enzyme. This thermo- and alkaline-stable enzyme demonstrated efficient decolorization of structurally different dyes, indicating its significant potential for industrial applications in textile dyeing effluent treatment.